1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and in particular, to a gear assembly to which power is easily and effectively transmitted from a main body of the image forming apparatus, and an optical photoconductive (OPC) drum unit provided with the gear assembly.
2. Description of the Related Art
In general, an OPC drum of a mono image forming apparatus is provided in one housing together with a developing roller, a toner transfer roller or the like, and a developing unit and an optical photoconductive (OPC) unit are not separately provided.
Therefore, a driving source of the OPC drum and a cleaning member for cleaning an electrification roller which electrifies the OPC drum, are usually fitted on the housing or other support member, and the developing member is driven by a separate driving source. In addition, waste toner is removed from the OPC drum by a cleaning blade, which is in contact with the OPC drum, and then freely drops; a waste toner transfer means is not separately provided.
In the case of recently developed color image forming apparatuses, an OPC unit and a developing unit are separately provided and the OPC unit comprises four color developing units, each for one of four colors, i.e., yellow, magenta, cyan and black.
Such color image forming apparatuses can be classified into a single path type and a multi-path type depending on the methods for forming and printing a color image on a recording medium.
A single path type image forming apparatus comprises a plurality of respective color developers and a plurality of OPC mediums. That is, a yellow developer, a magenta developer, a cyan developer and a black developer correspond to a first OPC medium, a second OPC medium, a third OPC medium and a fourth OPC medium, respectively, whereby individual color images are formed and then are transferred onto a single image transfer unit. Such a single path type image forming apparatus has an advantage in that the first to fourth OPC mediums can be constructed in a drum type that is easy to control rotational speed. However, because it is necessary to use a plurality of OPC mediums and to employ a plurality of laser scanning units (LSU), the volume of the image forming apparatus is increased and the price is high.
Contrary to this, in a multi-path type image forming apparatus, a plurality of developers selectively perform development on one OPC unit, in such a manner that during the first rotation of an OPC medium of the OPC unit, the yellow developer performs development, during the second rotation of the OPC medium, the magenta developer performs development, during the third rotation, the cyan developer performs development, and during the fourth rotation, the black developer performs development. Thereafter, an image, in which the colors are developed overlapping each other, is transferred to the image transfer unit at one time.
Such a multi-path type image forming apparatus has an advantage in that the entire volume can be reduced and the manufacturing costs can be lowered because only one OPC medium is used. However, because the OPC medium is formed in a belt type, there is a limit in properly controlling the rotational speed of the belt, and in the case of long-term use, the tension of the belt is weaken, whereby sometimes a defect may be caused in a color image.
Due to these problems of the prior art, there is a need to develop a drum type OPC medium to be used even in the multi-path type image forming apparatus. In particular, a need has been raised to develop an OPC unit in which yellow, magenta, cyan and black developers are fixed for stability in development, a cleaning roller that cleans an electrification roller and an auger that transfers waste are integrated within one OPC unit, and a power transmission system to effectively drive the cleaning roller and the auger.